Process for the chlorination of wool



United States Patent 0 PROCESS FOR THE CHLORINATION 0F WOOL KumataroHayashi, Suginami-ku, Tokyo-to, Japan, as-

signor to Daito Boshoku Kabushiki Kaisha (known as })aito WoolenSpinning & Weaving Co. Ltd.), Tokyo,

apan No Drawing. Filed May 28, 1957, Ser. No. 662,008 6 Claims. (Cl.8-128) This invention relates to improved processes for chlorinatingwool.

An object of this invention is to provide a process capable ofcontrolling the character and extent of the physical and chemical changeof the wool, thus rendering it the unshrinkable character.

A further object of this invention is to minimize the so-calledyellowing of the chlorinated wool.

Another object of this invention is to obtain the improved uniformity inthe chlorination of wool.

A still further object of this invention is to protect the wool from thereduction of its softness and touch.

Still another object of this invention is to minimize the alkali andacid solubilities of wool.

Said objects and other objects of this invention have been attained bythe process which comprises passing the wool to be treated through anacidic bath having a pH between 1 and 3 for a short time such as 10-50seconds so that the wool fibers may be made acidic in such a degree asto maintain the pH value of the chlorinating bath in the following stepat a value between 1 and 4; continuously introducing said pretreatedwool into a chlorinating bath and transferring it therethrough; andpouring a dilute aqueous solution of hypochlorite having a pH between 11and 6 on said pretreated wool at its posi tion being introduced into thechlorinating bath so that the chlorinating bath having a pH of 1-4 maybe established by instantaneous reaction of the poured liquor with theacid liberated from the wool fibers. The preferable quantity of thepouring chlorination liquor is about 10 to 25 times the dry weight ofthe wool under charging and the preferable quantity of the liquor in thechlorinating bath is about 10-25 times the weight of the wool immersedin the chlorinating bath.

In the well-known conventional processes for the chlorination of wooland more particularly in the Scholler process, is adopted the processwhich comprises subjecting the wool to be treated, after dipping thereofin an acidic bath for a long period of time such as about minutes, to anintermediate treatment for removing the excess amount of the acid tomoderate the acidity in the interior regions of the wool fibers to adegree suitable for the following step; and then subjecting saidintermediately treated wool fibers to chlorination by bringing saidfibers in contact with an alkaline chlorinating bath containingavailable chlorine of the combined form such as in calcium or sodiumhypochlorite, thus causing the gradual and controllable chlorination ofthe wool by the reaction of the hypochlorous acid with the acidcontained in the pretreated wool.

In the present invention, however, the preliminary acid treatment of thewool is carried out by passing continuously the wool fibers through anacidic bath of constant strength for a short time such as 10-50 secondsso that the wool fibers and particularly only the surface regions ofsaid fibers may be made acidic in such a degree as to maintain the pHvalue of the chlorinating bath in the following step at a value between1 and 4; and then the thus treated wool is immediately subjected tochlorination by pouring a chlorination liquor on said wool at itsposition being introduced into a chlorinating bath while transferringsaid wool through said bath so that the chlorinating bath having a pH of1-4 may be continuously established.

Accordingly, this invention differs substantially from theabove-mentioned conventional processes in its acid treatment and acidityof the chlorinating bath.

In the conventional processes, batch systems have been usedsubstantially for the chlorination of wool, but the process of thisinvention is carried out continuously, whereby an effective improvementof wool chlorination is made possible.

Furthermore, in the conventional processes, yellowing of the treatedwool is unavoidable; the chlorination is too intense to maintain theelasticity of the wool fibers in favourable condition; softness andnatural touch of the wool are reduced by the degradation caused by thetreatment; increase in alkali and acid solubilities of the wool due tochlorination is relatively large; decrease in dyeing afiinity due tochlorination is relatively large; and the treating cost is relativelyhigh.

According to the process of this invention, however, yellowing of thewool due to chlorination can be minimized or entirely avoided; strength,extensibility and elasticity of the wool are not unfavourably affectedby the chlorination; softness and natural touch of the wool are notaffected by the treatment; increase in alkali and acid solubilities ofthe wool due to chlorination can be minimized; fastness of the dyedcolours of the chlorinated wool is hardly decreased by sun-light,washing, friction and sweat; and the treating cost is relatively low.

The process of this invention is preferably applied to the wool ofsliver state, but may be applied also to the wool in the form of yarn orfabric.

In the embodiment of the process of this invention, dyeing can becarried out in any step of the manufacturing processes in wool industry,and it is of course permissible to carry out the dyeing prior to thechlorination, because variation of colour shade and decrease in thefastness of the dyed colour due to chlorination are negligible as longas the conventional dyes are used.

For the preparation of the acid bath of this invention, formic acid ispreferably used, and acetic acid, oxalic acid, sulphuric acid,hydrochloric acid, phosphoric acid, boric acid, etc. may be alsoapplied. Sometimes, any one of the anionic and non-ionic wetting agentsmay be preferably mixed in the acid for the uniform distribution of acidliquor on the wool fibers. Preferable pH value of the acidic bath is l-3and, more particularly, 1-2. It is preferable to carry out the acidtreatment of the wool for such a short time that only the surfaceregions of the wool fibers can be made acidic and the interior regionsthereof remain neutral.

As the chlorination agent in this invention, sodium hydrochlorite,calcium hypochlorite and other chlorineliberating agents may be used,but sodium hypochlorite can be advantageously applied for conditioningpH of the chlorination liquor. The pH value of the chlorination liquoris controlled at a value between 11 and 6. This liquor is poured on thepretreated wool at its position being introduced into the chlorinatingbath so that the chlorinating bath having a pH of 1-4 may becontinuously established by instantaneous reaction of the poured liquorwith the acid liberated from the surface regions of the wool fibers. Themost preferable quantity of the chlorination liquor to be poured on thewool is about 10 to 25 times the dry weight of said wool. The quantityof the available chlorine contained in the sodium hypochlorite iscontrolled within the range of 1.5 to 3.0% of the dry weight of the woolunder treatment in accordance with the degree of the chlorination. Theabove-mentioned pouring of the chlorination liquor is carried outcontinuously at one end of the chlorinating bath while charging thepretreated wool into said bath at the same end. The charged wool iscontinuously transferred toward the other end of said bath whilecompleting the chlorination thereof and then led out from said bath,thus eifectuating the continuous chlorination of the wool. In theprocess of this invention, for maintaining the pH value of thechlorinating bath at a constant value, it is extremely important tocontrol the quantity and the pH value of the chlorination liquor to bepoured, and the quantity of the available chlorine contained in thechlorinating bath and in the wool fibers. The pH value of thechlorinating bath should be maintained between 1 and 4 and thepreferable time interval of the chlorinating treatment should be about30 seconds. The wool thus chlorinated should be transferred as fast aspossible into the following dechlorinating bath.

In this invention, sodium thiosulfate or acidic sodium sulfite,preferably the former, may be used as the dechlorinating agent; 4-6%,particularly 5% solution of the former; 13%, particularly 2% solution ofthe latter may be recommended as said bath.

The dechlorination can be almost completed within the period of timebetween 30 seconds and one minute. The preferable quantity of thedechlorination liquor is from 100 parts to 400 parts per one part of thewool under treatment, but it may be more reduced as long as it issufficient for dipping the wool under treatment. The concentration ofthe dechlorinating bath should always be controlled suitably. For thewashing, a large quantity of the running water is used to carry outsuflicient washing and this washing should be carried out immediatelyafter the dechlorination. Since the chlorinated wool thus washed is yetacidic, its neutralization is necessary, so that the wool washed asdescribed above is treated with hot solution of synthetic washing agent,soap or sodium ash and then washed with hot water.

The wool thus treated by this invention receives no substantial changein physical and chemical properties of natural wool, and has noappreciable degradation such as yellowing and decrease in fastness ofdyed colour, and has an excellent unshrinkable property.

Example I The first step (acidificati0n).A continuous bundle of a numberof top slivers is passed for a short time through an acidic bathconsisting of a mixture of 2% solution of formic acid and a conventionalwetting agent of part of the weight of the formic acid, whilecontrolling the pH value of said mixture at a value between 1.8 and 2.0.By passing said bundle of slivers through said bath for a short timebetween and seconds, the acid is uniformly combined with only thesurfaces of the wool fibers, whereby it is made possible to make thecombined acid liberate easily and react with the pouring liquor in thenext step to prepare a favourable chlorinating bath. The quantity of theacidic bath liquor may be minimized within the range suitable for thesufiicient wetting of the wool fibers.

For maintaining the quantity of the acidic bath liquor, additionalportion corresponding to the loss of the liquor carried away by the woolfibers must be successively added to the bath.

The second step (chlorinated).--The wool which has been treated in thefirst step is introduced into a chlorinating bath at one end thereof andcontinuously transferred toward the other end of said bath and then ledout from the latter end. A solution of sodium hypochlorite iscontinuously poured on said wool at its position being introduced intothe chlorinating bath. By the action of the chlorine liberated from thechlorinating agent due to the reaction of said agent with the acidliberated from the surfaces of the wool fibers, chlorination of the woolis completed within a period of time between 20 and 40 seconds. The thuschlorinated wool led out from the chlorinating bath is then introducedinto a dechlorinating bath in the third step. The pH value of thechlorinating bath must be maintained within the range of l-4 and thequantity of the chlorinating agent is controlled so that the quantity ofthe available chlorine contained in said agent may be 13% of the dryweight of the wool under charging.

The third step (dechl0rinati0n).The completely chlorinated wool ispassed through 5% solution of sodium thiosulfate or 2% solution ofanhydrous sodium sulfite to subject said wool to dechlorination toremove the nonreacted chlorine from the surfaces of the wool fibers.This treatment is carried out for a time within the range between 30 and60 seconds. The consumed quantity of the dechlorinating agent ismeasured by the iodometry and supplemented now and then.

The fourth step (neutralization and washing).-After the dechlorination,the treated wool is subjected to neutralization and washing with waterin the conventional methods.

The final wool obtained by the process of this example showsapredominant resistance to laundry shrinkage, that is to say, itswashability is very high. For example, when soaking characters of twopatterns of the same fabric were tested five times with 0.5% solution ofsoap, at a temperature of 65 C., for 30 minutes and the tested fabricswere measured by a Lavado Meter, the shrinkage of the fabric treatedaccording to this invention was below 5%, but that of the fabric nottreated was about 27%.

Example I] In this example, an inorganic mineral acid is used in thefirst step and a conventional non-ionic wetting agent is mixed in thechlorination liquor in the second step, whereby the chlorination of thewool in the chlorinating bath is made more uniform.

The first step (acidificati0n).-A continuous bundle of a number of topslivers is passed through an acidic bath for a time between 20 and 30seconds, as in the case of the Example I. In this example, an acidicbath consisting of a mixture of 1-1.5% solution of sulfuric acid and aconventional anionic wetting agent of part of the weight of saidsolution is used. By passing said bundle of slivers through said bath,the surfaces of the wool fibers are made acidic uniformly within a shorttime between 65 and 30 seconds.

The pH value of the acidic bath may be varied somewhat depending uponthe kind of the wetting agent to be mixed, but it is maintained at avalue between 1 and 1.2 in this example.

Since said acidification completes within a short time between 20 and 30seconds, chemical combination of the acid with the wool fibers hardlyoccurs and only the surfaces of the wool fibers are made acidicuniformly, whereby control of the pH value of the chlorinating bath inthe second step is made very easy.

The second step (chl0rinati0n).--The sliver having been treated in thefirst step is introduced into a chlorinating bath at one end thereof andcontinuously transferred therethrough toward the other end of said bathand then led out. A chlorinating solution as illustrated already iscontinuously poured on the wool at its position being introduced intothe chlorinating bath. By the action of the chlorine liberated from thechlorinating agent due to the reaction of said agent with the acidliberated from the surfaces of the slivers, chlorination of the woolslivers is completed during its transference through the chlorinatingbath and within a period between 20 and 40 seconds. The pH value of thechlorinating bath is maintained at a value between 2 and 3. In thisexample, a non-ionic wetting agent of 0.01% of the weight of said bathliquor is mixed in the chlorinating agent, whereby particularly uniformchlorination of the slivers is made to occur.

When an inorganic mineral acid is used in the first step, the liberationof chlorine gas is made very rapid as compared with the case of theExample I. Accordingly, it is preferable to add a non-ionic wettingagent in the second step to obtain an effective and uniformchlorination;

The third step (dechl0rinati0n).-The chlorinated wool is passed through2% solution of sodium sulfate to subject said wool to dechlorination toremove the nonreacted chlorine from the surfaces of the wool fibers. Thetime for the dechlorination is preferably 30 seconds.

The fourth step (neutralization and washing).-This step is entirely sameas the Example I.

While I have described particular embodiments of my invention, it will,of course, be understood that I do not wish my invention to be limitedthereto, since many modifications may be made and I, therefore,contemplate by the appended claims to cover all such modifications asfall within the true spirit and scope of my invention.

I claim:

1. A process for the chlorination of wool which comprises passing thewool to be treated through an acidic bath having a pH between 1 and 3for a short time of the order of -50 seconds so that the wool fiberswill be made acidic to a degree sufficient to maintain the pH value ofthe chlorinating bath in the following step at a value between 1 and 4;continuously introducing said pretreated wool without interveningchemical treatment into a chlorinating bath at one end thereof andtransferring it therethrough toward the other end; and distributing adilute aqueous solution of hypochlorite having a pH between 11 and 6 onsaid pretreated wool as it is being introduced into the chlorinatingbath so that a pH of 1 to 4 will be established in the chlorinating bathby instantaneous reaction of the distributed hypochlorite solution withthe acid liberated from the wool fibers, whereby said chlorinating bathin which said wool is immersed has a pH of l to 4 throughout thechlorination of said wool.

2. A process for the chlorination of wool which comprises passing thewool to be treated through an acidic bath having a pH between 1 and 3for a short time of the order of 10-50 seconds so that the wool fiberswill be made acidic to a degree sufiicient to maintain the pH value ofthe chlorinating bath in the following step at a value between 1 and 4;continuously introducing said pretreated wool without interveningchemical treatment into a chlorinating bath at one end thereof andtransferring it therethrough toward the other end; and distributing adilute aqueous solution of hypochlorite having a pH between 11 and 6 onsaid pretreated wool as it is being introduced into the chlorinatingbath so that a pH of 1 to 4 will be established in the chlorinating bathby instantaneou reaction of the distributed hypochlorite solution withthe acid liberated from the wool fibers, whereby said chlorinating bathin which said wool is immersed has a pH of 1 to 4 throughout thechlorination of said wool, the quantity of the distributed hypochloritesolution being about 10 to 25 times the dry weight of the wool beingcharged and the quantity of the liquor in the chlorinating bath beingabout 10-25 times the weight of the wool immersed in the chlorinatingbath.

3. A process for the chlorinating of wool which comprises passing thewool to be treated through an acidic bath having a pH of 2 for a shorttime of the order of 10-50 seconds so that the wool fibers will be madeacidic to a degree sufiicient to maintain the pH value of thechlorinating bath in the following step at a value between 1 and 4;continuously introducing said pretreated wool without interveningchemical treatment into a chlorinating bath at one end thereof andtransferring it therethrough toward the other end; and distributing adilute aqueous solution of hypochlorite having a pH between 11 and 6 onsaid pretreated wool as it is being introduced into the chlorinatingbath so that a pH of 1 to 4 will be established in the chlorinating bathby instantaneous reaction of the distributed hypochlorite solution withthe acid liberated from the wool fibers, whereby said chlorinating bathin which said wool is immersed has a pH of 1 to 4 throughout thechlorination of said wool, the quantity of the distributed hypochloritesolution being about 10 to 25 times the dry weight of the wool beingcharged and the quantity of the liquor in the chlorinating bath beingabout 10 to 25 times the weight of the wool immersed in the chlorinatingbath.

4. A process for the chlorination of wool which comprises passing thewool to be treated through an acidic bath having a pH between 1 and 3for a short time of the order of 10-50 seconds so that only the surfaceregions of the Wool fibers will be made acidic to a degree sufiicient tomaintain the pH value of the chlorinating bath in the following step ata value between 1 and 4; continuously introducing said pretreated Woolwithout intervening chemical treatment into a chlorinating bath at oneend thereof and transferring it therethrough toward the other end; anddistributing a dilute aqueous solution of hypochlorite having a pHbetween 11 and 6 on said pretreated wool as it is being introduced intothe chlorinating bath so that a pH of 1 to 4 will be established in thechlorinating bath by instantaneous reaction of the distributedhypochlorite solution with the acid liberated from the surface regionsof the wool fibers, whereby said chlorinating bath in which said wool isimmersed has a pH of l to 4 throughout the chlorination of said Wool,the quantity of the distributed hypochlorite being about 10 to 25 timesthe dry weight of the wool being charged and the quantity of the liquorin the chlorinating bath being about 1025 times the weight of the woolimmersed in the chlorinating bath.

5. A process for the chlorination of wool which comprises passing thewool to be treated through formic acid bath having a pH between 1 and 3for a short time of the order of 10-50 seconds so that only the surfaceregions of the wool fibers will be made acidic to a degree suflicient tomaintain the pH value of the chlorinating bath in the following step ata value between 1 and 4; continuously introducing said pretreated woolwithout intervening chemical treatment into a chlorinating bath at oneend thereof and transferring it therethrough toward the other end; anddistributing a dilute aqueous solution of sodium hypochlorite containingthe combined available chlorine of an amount sufficient to thechlorinating reaction and having a pH between 11 and 6 on saidpretreated Wool as it is being introduced into the chlorinating bath sothat a pH of l to 4 will be established in the chlorinating bath 'byinstantaneous reaction of the distributed hypochlorite solution with theacid liberated from the surface regions of the wool fibers, whereby saidchlorinating bath in which said wool is immersed has a pH of 1 to 4throughout the chlorination of said wool, the quantity of thedistributed hypochlorite solution being about 10 to 25 times the dryweight of the wool being charged and the quantity of the liquor in thechlorinating bath being about 10-25 times the weight of the woolimmersed in the chlorinating bath.

- 6. A process for the chlorination of wool which comprises passing thewool to be treated through a formic acid bath having a pH between 1 and3 for a short time of the order of 1050' seconds so that only thesurface regions of the wool fibers will be made acidic to a degreesufficient to maintain the pH value of the chlorinating bath in thefollowing step at a value between 1 and 4; continuously introducing saidpretreated wool without intervening chemical treatment into achlorinating bath at one end thereof and transferring it therethroughtoward the other end; and distributing a dilute aqueous solution ofsodium hypochlorite containing the combined available chlorine of 1.5 to3%, by weight, of said solution and having a pH between 11 and 6 on saidpretreated W001 as it is being introduced into the chlorinating bath sothat a pH of 1 to 4 will be established in the chlorinating bath byinstantaneous reaction of the distributed hypochlorite solution with theacid liberated from the surface regions of the wool fibers, whereby saidchlorinating bath in which said wool is immersed has a pH of 1 to 4throughout the chlorination of said wool, the quantity of thedistributed hypochlorite solution being about 10 to 25 times the dryweight of the wool being charged and the quantity of the liquor in thechlorinating bath being about 10- 25 times the weight of the woolimmersed in the chlorinating bath.

8 References Cited in the file of this patent UNITED STATES PATENTS2,326,021 Ericsson Aug. 3, 1943 2,702,737 Koons et a1. Feb. 22, 1955FOREIGN PATENTS 683,762 Great Britain Dec. 3, 1952 OTHER REFERENCESMoncrieif: Wool Shrinkage, The National Trade Press, Ltd., London(1953), pp. 219221.

1. A PROCESS FOR THE CHLORINATION OF WOOL WHICH COMPRISES PASSING THEWOOL TO BE TREATED THROUGH AN ACIDIC BATH HAVING A PH BETWEEN 1 AND 3FOR A SHORT TIME OF THE ORDER OF 10-50 SECONDS SO THAT THE WOOL FIBERSWILL BE MADE ACIDIC TO A DEGREE SUFFICIENT TO MAINTAIN THE PH VALUE OFTHE CHLORINATING BATH IN THE FOLLOWING STEP AT A VALUE BETWEEN 1 AND 4:CONTINUOUSLY INTRODUCING SAID PRETREATED WOOL WITHOUT INTERVENINGCHEMICAL TREATMENT INTO A CHLORINATING BATH AT ONE END THEREOF ANDTRANSFERRING IT THERETHROUGH TOWARD THE OTHER END, AND DISTRIBUTING ADILUTE AQUEOUS SOLUTION OF HYPOCHLORITE HAVING A PH BETWEEN 11 AND 6 ONSAID PRETREATED WOOL AS IT IS BEING INTRODUCED INTO THE CHLORINATINGBATH SO THAT A PH OF 1 TO 4 WILL BE ESTABLISHHED IN THE CHLORINATINGBATH BY INSTANTANEOUS REACTION OF THE DISTURBED HYPOCHLORIDE SOLUTIONWITH THE ACID LIERATED FROM THE WOOL FIBERS, WHEREBY SAID DICORINATINGBATH IN WHICH SAID WOOL IS IMMERSED HAS A PH OF 1 TO 4 THROUGHOUT THECHLORINATION OF SAID WOOL.